1. Field of the Invention
The present invention relates to systems and methods for protecting vehicle occupants from injury. More specifically, the present invention relates to a dual flow inflator that injects multiple gas flows into an airbag system, such as an inflatable curtain.
2. Description of Related Art
The inclusion of inflatable safety restraint devices, or airbags, is now a legal requirement for many new vehicles. Airbags are typically installed in the steering wheel and in the dashboard on the passenger side of a car. In the event of an accident, an accelerometer within the vehicle measures the abnormal deceleration and triggers the expulsion of rapidly expanding gases from an inflator. The expanding gases fill the airbags, which immediately inflate in front of the driver and passenger to protect them from impact against the windshield. Side impact airbags, known as inflatable curtains, have also been developed in response to the need for protection from impacts in a lateral direction, or against the side of the vehicle. An inflatable curtain may have one or more separately inflated cushions.
Side impact cushions are often designed to unfold or unroll downward to inflate beside a person to keep the person from hitting the door or window during lateral impact. Since a vehicle occupant may be leaning forward, reclined in the seat, or at any position between, such cushions are often made somewhat long to ensure that the occupant hits the cushion. If multiple cushions are fed by a single inflator positioned either fore or aft of the cushions, an especially long gas flow path exists between the inflator and the cushion furthest from the inflator. Thus, the outermost extents of the inflatable curtain may receive insufficient inflation gas pressure to inflate to the optimal protective pressure.
Even with somewhat shorter cushions, rapid and even inflation can be difficult to achieve with known inflator designs. Many existing inflators eject inflation gases outward radially; consequently, the inflation gases are not propelled along the length of the cushion, but are directed into the cushion near the inflator. The outer regions of the cushion are still inflated later than those closest to the inflator.
Additionally, some inflatable curtain systems are somewhat expensive due to the need for multiple inflators, attachment mechanisms, and the like. Many inflatable curtain systems require the use of a gas conduit that conveys gas from the inflator to the inflatable curtain. Some known inflators require the use of multiple initiators that add to the manufacturing expense and timing requirements of the inflator.
Furthermore, many inflators produce thrust upon activation. As a result, somewhat complex attachment mechanisms must often be used to affix the inflators to the vehicle to ensure that the inflators do not dislodge themselves during deployment. Such additional parts increase the cost of the inflatable curtain system, as well as the time and expense required to install the inflatable curtain system in a vehicle.
Accordingly, a need exists for an inflator and related methods that remedy the problems found in the prior art. Such an inflator should preferably provide relatively even and rapid inflation of the associated inflatable curtain, preferably without requiring multiple inflators for a single curtain. Such an inflator should also preferably be simple and inexpensive to manufacture and install.
The apparatus of the present invention has been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available inflators. Thus, it is an overall objective of the present invention to provide an inflator and related systems and methods that provides rapid, even inflation with a minimum of manufacturing and installation cost.
To achieve the foregoing objective, and in accordance with the invention as embodied and broadly described herein in the preferred embodiment, a dual flow inflator is provided. According to one configuration, the inflator may comprise a gas chamber with a first end disposed within a first inlet port of the inflatable curtain and a second end disposed within a second inlet port of the inflatable curtain. The gas chamber may comprise one unitary body. The first and second inlet ports may be tightly affixed to the gas chamber such that gas is unable to escape from the inflatable curtain between the inlet ports and the gas chamber.
The gas chamber may have a first exit orifice positioned at the first end and a second exit orifice positioned at the second end. Each exit orifice may have a sealed configuration that does not permit gas flow, and an open configuration, in which inflation gases flow relatively freely out of the gas chamber through the exit orifice. Each exit orifice may take the form of a diffuser that forms an interior wall with an opening covered by a burst disc; the burst discs may be removed from the openings via a pressure shock induced by combustion within the gas chamber. Burst disc retention members may be disposed outside the openings to capture the burst discs and ensure that they do not damage the inflatable curtains.
Each exit orifice may also have a gas guide diffuser disposed outside the opening to control the flow of inflation gas out of the exit orifice. The gas guide diffusers may be aligned with the longitudinal axis of the inflator so that inflation gases are ejected along the longitudinal axis. The gas guide diffusers of the first and second orifices may be directed opposite to each other so that thrust from the first exit orifice substantially negates the thrust from the second exit orifice, and vice versa.
The inflator may have an initiator disposed near or partially within the gas chamber to activate a gas-producing material to create first and second gas flows through the first and second exit orifices, respectively. The gas-producing material may be a liquid/gas mixture that has been cryogenically inserted into the gas chamber in solid form. Whether cryogenic or standard gas-producing material is used, the gas-producing material may be inserted into the inflator through a sealable fill port or into the interior of the inflator prior to assembly of the inflator components. The initiator may heat the liquid/gas mixture to cause the pressure shock that removes the burst discs from the openings, thereby moving the first and second exit orifices into the open configuration.
According to one alternative embodiment, an inflator may comprise a gas chamber constructed of multiple parts. The gas chamber may have two vessels and a bulkhead. Each of the vessels may have a generally tubular shape with an interior end and an exterior end. The bulkhead may also have a tubular shape with two apertures designed to be aligned with the interior ends of the vessels. The vessels may be affixed to the bulkhead through a method such as welding. First and second exit orifices may be disposed on the exterior ends of the first and second vessels, respectively.
In place of the openings and burst discs of the first embodiment, the first and second exit orifices of the second embodiment may take the form of scored, or notched, surfaces that open when the pressure within the gas chamber exceeds the tear strength of the scored regions. The scored surface may open to form a suitable exit nozzle.
As with the previous embodiment, a gas-producing material such as a compressed gas and liquid mixture may be thermally activated by an initiator to provide first and second gas flows through the first and second exit orifices, respectively. In order to ensure that both scored surfaces burst completely and simultaneously, two pistons may be positioned within the gas chamber on either side of the initiator. When the gas-producing material between the pistons expands, the increasing pressure drives the pistons outward, toward the exit orifices. The result is an increase in the pressure between the pistons and the exit orifices; this pressure increase induces failure of the scored regions to open the first and second exit orifices.
According to another alternative, the inflator may comprise a gas chamber with two vessels affixed to a generally spherical bulkhead. Each vessel may have an exit orifice that takes the form of a compression closure, such as a crimped opening. The crimped opening may have two lips pressed flat together and attached through a method such as welding. As with the scored region, the crimped opening opens in response to a pressure increase within the gas chamber. In the alternative, some physical puncture mechanism may be used to open the crimped opening when activated by the initiator.
More specifically, the inflator may have pistons like those described in connection with the previous embodiment. Each of the pistons may have a puncture member designed to impact the associated exit orifice, thereby opening the lips to permit escape of the pressurized inflation gases.
In yet another embodiment, the entire gas chamber may have a generally spherical shape. The gas chamber may be made from two hemispherical portions attached together. Each hemispherical portion may have an exit orifice; the exit orifices may be positioned opposite each other to permit the inflation gases to flow out from the gas chamber in opposite directions. The exit orifices may take the form of openings with burst discs, as in the first embodiment.
Through the use of the inflators of the present invention, cost savings may be obtained through the elimination of gas conduits, complex attachment features, and redundant inflators and initiators. Additionally, more rapid and even inflation of the inflatable curtains may be obtained. As a result, the availability and effectiveness of vehicular airbag systems may be enhanced.
These and other objects, features, and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.